Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D213/00—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members
  • C07D213/02—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members
  • C07D213/04—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members having no bond between the ring nitrogen atom and a non-ring member or having only hydrogen or carbon atoms directly attached to the ring nitrogen atom
  • C07D213/60—Heterocyclic compounds containing six-membered rings, not condensed with other rings, with one nitrogen atom as the only ring hetero atom and three or more double bonds between ring members or between ring members and non-ring members having three double bonds between ring members or between ring members and non-ring members having no bond between the ring nitrogen atom and a non-ring member or having only hydrogen or carbon atoms directly attached to the ring nitrogen atom with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms
  • C07D213/61—Halogen atoms or nitro radicals

Definitions

• the present invention relates to a new process for the preparation of substituted 2-chloropyridines.
• 2-chloro-5-methyl-pyridine is obtained (besides 2-chloro-3-methyl-pyridine, 4-chloro-3-methylpyridine and 3-chloro-5-methyl-pyridine) on reacting 3-methyl-pyridine 1-oxide with phosphoryl chloride (cf. Weissberger, Chemistry of Heterocyclic Compounds, Pyridine and its Derivatives, Vol. 14, Supplement, Part 2, p. 112, publisher John Wiley & Sons, New York, 1974).
• the main product of this reaction is 4-chloro-3-methylpyridine; the amount of 2-chloro-5-methyl-pyridine is generally less than 25%
• R 1 represents hydrogen, chlorine, cyano, carbalkoxy-(C 1 -C 4 ) or ##STR4## where R 5 and R 6 are identical or different and represent hydrogen or alkyl (C 1 -C 4 ),
• R 2 represents hydrogen, chlorine, alkyl(C 1 -C 4 ), halogenoalkyl(C 1 -C 4 ), cyanoalkyl(C 1 -C 4 ), alkoxy(C 1 -C 4 )-alkyl(C 1 -C 4 ), dialkylamino(C 1 -C 4 )alkyl(C 1 -C 4 ), carbalkoxy(C 1 -C 4 ) or ##STR5## where R 5 and R 6 are identical or different and represent hydrogen or alkyl (C 1 -C 4 )
• R 1 and R 2 together represent the bivalent group --CH ⁇ CH--CH ⁇ CH--
• R 3 represents hydrogen, chlorine, carbalkoxy(C 1 -C 4 ) or ##STR6## where R 5 and R 6 are identical or different and represent hydrogen or alkyl (C 1 -C 4 ), and
• R 4 represents hydrogen, chlorine or cyano
• R 3 and R 4 together represent the bivalent group --CH ⁇ CH--CH ⁇ CH--.
• R 1 , R 2 , R 3 and R 4 have the abovementioned meaning are reacted with a chlorine-containing phosphoric acid derivative from the series of the chlorophosphoric esters and chlorophosphoramides in the presence of an inert organic solvent and in the presence of an acid acceptor at temperatures between -20° C. and 200° C., and the resulting product is separated further, if appropriate.
• the starting materials pyridine 1-oxides of the formula (II) and chlorophosphoric esters or chlorophosphoramides are known compounds of organic chemistry or can be prepared by known processes. See, for example:
• Formula (II) provides a general definition of the substituted pyridine 1-oxides which are employed as starting substances for the process according to the invention.
• R 1 preferably represents hydrogen, chlorine, cyano, COOCH 3 , COOC 2 H 5 , CON(CH 3 ) 2 and CON(C 2 H 5 ) 2 ,
• R 2 preferably represents hydrogen, chlorine, CH 3 , C 2 H 5 , CH 2 Cl, CH 2 CN, CH 2 --OCH 3 , CH 2 --OC 2 H 5 , CH 2 --N(i--C 3 H 7 ) 2 , CH 2 --N(i--C 4 H 9 ) 2 , COOCH 3 , COOC 2 H 5 , CON(CH 3 )CH 2 and CON(C 2 H 5 ) 2 ,
• R 3 preferably represents hydrogen, chlorine, COOCH 3 , COOC 2 H 5 , CON(CH 3 ) 2 and CON(C 2 H 5 ) 2 or
• R 1 and R 2 in each case together represent the bivalent group --CH ⁇ CH--CH ⁇ CH--and
• R 4 preferably represents hydrogen, chlorine or cyano, or R 3 and R 4 in each case together represent the bivalent group --CH ⁇ CH--CH ⁇ CH--.
• the chlorine-containing phosphoric acid derivatives from the series of the chlorophosphoric esters and chlorophosphoramides which are employed in the process according to the invention preferably are from the following classes of compounds:
• N,N-dialkyl(C 1 -C 4 )-chlorophosphoramides and, in particular, N,N-dimethyl-dichlorophosphoramide,N,N-diethyldichlorophosphoramide, N,N-dipropyl-dichlorophosphoramide, N,N-diisopropyl-dichlorophosphoramide, N,N-dibutyl-dichlorophosphoramide and N,N-diisobutyl-dichlorophosphoramide, and
• alkyl(C 1 -C 6 ) chlorophosphoric esters and, in particular, methyl dichlorophosphate, ethyl chlorophosphate, propyl dichlorophosphate, isopropyl dichlorophosphate, butyl dichlorophosphate, isobutyl dichlorophosphate, tert.-butyl dichlorophosphate, pentyl dichlorophosphate and hexyl dichlorophosphate.
• solvents which are suitable for this purpose are virtually all inert organic solvents. These preferably include aliphatic or aromatic hydrocarbons, such as pentane, hexane, heptane, octane, cyclohexane, methylcyclohexane, petroleum ether, benzine, ligroin, benzene, toluene, xylene and tetralin, halogenated hydrocarbons, such as methylene chloride, ethylene chloride, trichloroethylene, chloroform, carbon tetrachloride, chlorobenzene and dichlorobenzene, ethers, such as diethyl ether, dipropyl ether, diisopropyl ether, dibutyl ether, methyl tert-butyl ether, glycol dimethyl ether, diglycol dimethyl ether, tetrahydrofuran and
• Particularly preferred organic solvents are methylene chloride, chloroform and chlorobenzenes.
• An acid acceptor which is preferably suitable is a basic nitrogen compound.
• Preferred basic nitrogen compounds are dialkylamines, such as, for example, diethylamine, dipropylamine, dibutylamine, diisobutylamine and di-sec-butylamine, trialkylamines, such as, for example, triethylamine, tripropylamine and tributylamine, dialkylcycloalkylamines, such as, for example, dimethyl-cyclopentylamine, diethyl-cyclopentylamine, dimethyl-cyclohexylamine and diethylcyclohexylamine, or dialkylaralkylamines, such as, for example, dimethylbenzylamine and diethylbenzylamine, and dialkylarylamines, such as, for example, dimethylaniline, and also pyridine derivatives, such as 2,6-dimethylpyridine and 2,4,6-
• diisopropylamine is particularly preferred.
• the process according to the invention is carried out in a temperature range between -20° C. and 200° C., preferably at temperatures between 0° C. and 150° C.
• the process according to the invention is generally carried out under atmospheric conditions. However, it is also possible to carry out the process under increased or reduced pressure between 0.1 and 10 bar.
• between 1 and 10 moles, preferably between 1 and 2 moles, of chlorophosphoric ester or chlorophosphoramide, and also between 1 and 10 moles, preferably between 1 and 2 moles, of the basic organic nitrogen compound are generally employed per mole of substituted pyridine 1-oxide of the formula (II). It is particularly preferred to employ approximately 1.5 moles of chlorophosphoric ester or chlorophosphoramide and nitrogen compound in each case per mole of substituted pyridine-N-oxide.
• the mixture can be worked up in the customary manner.
• the reaction mixture is preferably (a) distilled, (b) extracted or (c) treated with water, the organic solvent is removed, for example by distillation, the aqueous phase is adjusted to a pH of 6 using an aqueous alkali metal hydroxide solution or alkaline earth metal hydroxide solution, such as, for example, sodium hydroxide solution, and most of the reaction product is removed from this mixture by steam distillation.
• the organic phase of the steam distillate essentially contains the product of the formula (I).
• the pure compound of the formula (I) can be prepared from the organic phase of the steam distillate by customary methods, for example by fine-distillation on a packed column.
• the overall yield in the preparation of 2-chloro-5-methyl-pyridine, starting from 3-methyl-pyridine 1-oxide, is 70 to 83% of theory.
• 2-Chloro-5-methylpyridine which can be prepared by the process according to the invention, is known as an intermediate for medicaments (cf. DE-A 2,812,585).
• 2-Chloro-5-methyl-pyridine can furthermore be employed as an intermediate for the preparation of insecticidal nitromethylene derivatives (cf. EP-A 163,855).
• the pure 2-chloro-5-methylpyridine can be separated off by fractional distillation.
• the mixture is heated for 2 hours at 60° C. and the diisopropylamine hydrochloride is filtered off with suction and washed with 50 ml of chlorobenzene.
• the filtrate is stirred for 1 hour with 200 ml of half-concentrated hydrochloric acid, and the aqueous phase is then adjusted to pH 6 using concentrated sodium hydroxide solution and extracted twice using 100 ml of toluene each time. After the solvent has been distilled off, 31.1 g of a mixture of 81% of 2-chloro-5-methylpyridine and 19% of 2-chloro-3-methylpyridine are obtained.

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Citations (7)

• 1988
  • 1988-11-22 DE DE3839332A patent/DE3839332A1/de not_active Withdrawn
• 1989
  • 1989-11-01 US US07/430,389 patent/US5010201A/en not_active Expired - Lifetime
  • 1989-11-09 DE DE8989120763T patent/DE58904566D1/de not_active Expired - Fee Related
  • 1989-11-09 EP EP89120763A patent/EP0370317B1/de not_active Expired - Lifetime
  • 1989-11-20 KR KR1019890016795A patent/KR0139639B1/ko not_active IP Right Cessation
  • 1989-11-21 JP JP1300927A patent/JP2806998B2/ja not_active Expired - Fee Related

Patent Citations (7)

Non-Patent Citations (10)

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